Book Review: The theory that would not die: how Bayes' rule cracked the enigma code, hunted down Russian submarines, and emerged triumphant from two centuries of controversy, by Sharon Bertsch McGrayneA mathematical theory about conditional and inverse probabilities seems one of the less likely subjects for a popular science book; indeed, there is so little about mathematics in this book that I am left little wiser about the theory itself, though there is an appendix that gives a useful though very brief example. For the most part this is a qualitative history of applications of Bayes' theorem, with a sideline theme of the somewhat undignified academic arguments around its merits. There's some interesting material on the history of insurance premium calculations, and certainly the section on Bletchley Park and decryption of the Enigma and Fish codes is particularly well done. My prior knowledge of Bayes was limited to knowing it was used in spam filtering, and although that's mentioned, it doesn't go into much detail on that subject (though there's an interesting aside about Microsoft's dreaded Paper Clip).